Re: [Xen-devel] Re: [PATCH 08/23] xen: statically initialize cpu_evtchn_mask_p

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-02-09 at 13:42 +0000, Andrew Jones wrote:
> On 01/25/2011 03:02 PM, Ian Campbell wrote:
> > On Mon, 2011-01-24 at 17:44 +0000, Paolo Bonzini wrote:
> >> On 10/12/2010 05:44 PM, Konrad Rzeszutek Wilk wrote:
> >>> -static struct cpu_evtchn_s *cpu_evtchn_mask_p;
> >>> +
> >>> +static __initdata struct cpu_evtchn_s init_evtchn_mask = {
> >>> + .bits[0 ... (NR_EVENT_CHANNELS/BITS_PER_LONG)-1] = ~0ul,
> >>> +};
> >>> +static struct cpu_evtchn_s *cpu_evtchn_mask_p =&init_evtchn_mask;
> >>> +
> >>>   static inline unsigned long *cpu_evtchn_mask(int cpu)
> >>>   {
> >>>           return cpu_evtchn_mask_p[cpu].bits;
> >>
> >> This causes a modpost warning:
> >>
> >>     WARNING: drivers/xen/built-in.o(.data+0x0): Section mismatch in
> >>     reference from the variable cpu_evtchn_mask_p to the variable
> >>     .init.data:init_evtchn_mask
> >>
> >>     The variable cpu_evtchn_mask_p references
> >>     the variable __initdata init_evtchn_mask
> >>
> >>     If the reference is valid then annotate the
> >>     variable with __init* or __refdata (see linux/init.h) or name the 
> >> variable:
> >>     *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, 
> >> *_console, 
> >>
> >> This is harmless, the variable is initialized to non-init data
> >> in an __init function.  The added noise is ugly, though.
> > 
> > Does this help? If I understand the comment which precedes  __initref
> > correctly it is intended to address precisely this situation.
> > 
> > Ian.
> > 8<---------
> > 
> > xen: events: mark cpu_evtchn_mask_p as __refdata
> > 
> > This variable starts out pointing at init_evtchn_mask which is marked
> > __initdata but is set to point to a non-init data region in xen_init_IRQ
> > which is itself an __init function so this is safe.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > 
> > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > index 31af0ac..5061af0 100644
> > --- a/drivers/xen/events.c
> > +++ b/drivers/xen/events.c
> > @@ -114,7 +114,7 @@ struct cpu_evtchn_s {
> >  static __initdata struct cpu_evtchn_s init_evtchn_mask = {
> >     .bits[0 ... (NR_EVENT_CHANNELS/BITS_PER_LONG)-1] = ~0ul,
> >  };
> > -static struct cpu_evtchn_s *cpu_evtchn_mask_p = &init_evtchn_mask;
> > +static struct __refdata cpu_evtchn_s *cpu_evtchn_mask_p =
> > &init_evtchn_mask;
> >  
> >  static inline unsigned long *cpu_evtchn_mask(int cpu)
> >  {
> > 
> 
> This does indeed fix it. Although you need __refdata to follow the
> complete struct name 'struct cpu_evtchn_s' rather than just 'struct', i.e.
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 7468147..a313890 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -114,7 +114,7 @@ struct cpu_evtchn_s {
>  static __initdata struct cpu_evtchn_s init_evtchn_mask = {
>         .bits[0 ... (NR_EVENT_CHANNELS/BITS_PER_LONG)-1] = ~0ul,
>  };
> -static struct cpu_evtchn_s *cpu_evtchn_mask_p = &init_evtchn_mask;
> +static struct cpu_evtchn_s __refdata *cpu_evtchn_mask_p =
> &init_evtchn_mask;
> 
>  static inline unsigned long *cpu_evtchn_mask(int cpu)
>  {
> 
> 
> Ian, are you going to push this to lkml in one of your batches?

Sure.

Can I add an Acked- and/or Tested-by from you?

Ian.



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